Increased prevalence of obstructive sleep apnea in patients with Cushing's syndrome compared with weight-and age-matched controls

Objective: Diabetes mellitus and obesity are well-known risk factors associated with obstructive sleep apnea (OSA). Cushing's syndrome (CS) is also characterized by obesity and diabetes mellitus. However, the association between CS and OSA remains unclear. Therefore, we investigated the possible associations between CS and OSA in this study. Patients and methods: Thirty female patients with newly diagnosed active CS and 30 age-,gender-and body mass index (BMI)-matched controls were included in this study. All participants were evaluated by overnight polysomnography. OSA was defined as having an apnea-hypopnea index (AHI) score of >= 5 events/h. Insulin resistance was calculated by homeostasis model assessment (HOMA) scores. Fasting serum cortisol was also determined. Results: The prevalence of OSA was higher (50% vs 23%, P = 0.003) in patients with CS compared with the control subjects. The mean HOMA (P = 0.046) and AHI (P = 0.028) scores were higher in patients with CS compared with the control subjects. AHI was positively correlated with the HOMA scores (r = 0.281, P = 0.046) in both groups. Linear regression analysis showed that serum cortisol remained as an independent predictor for AHI after controlling for BMI and HOMA score (P< 0.001). Conclusions: The prevalence of OSA increased in patients with CS compared with control subjects with similar ages and BMI levels. Hypercortisolemia is an independent risk factor for developing OSA. The presence of OSA needs to be considered in patients with CS.